The present invention relates in general to auto stop-start equipped vehicles and power management of high load devices during engine auto stop-start operations.
Vehicles typically utilize a single 12V battery topology as a vehicle's power source; however, such systems have limited charge power capability. With the increasing demand of electric power in modern day vehicles, there is an increasing challenge to utilize all possible power sources that generate energy in the vehicle and maximize the use of these generated energy devices or systems. The maximum amount of energy that can be stored in such devices determines how other devices may be used or when energy can be provided to such devices.
Vehicles capable of performing an engine stop-start operation utilize an internal combustion engine that is turned off when the vehicle is at an idle status. This allows these vehicles to reduce emissions and save on fuel economy since the internal combustion engine is not operating during an auto stop period. Once the auto-stop period has ended, the internal combustion engine is re-started utilizing an auto start operation. Many auto stop-start equipped vehicles primarily use a single battery as their power source. Due to the fact that the single battery has limited power, the energy management system must make sure that a sufficient amount of energy is still present in the battery when the internal combustion engine is re-started during a stop-start operation. Other features that may be pertinent to operate during the period when the internal combustion engine is temporarily turned off are electrical load devices, particularly those that require increased energy draw that may deplete the battery to a point where engine re-start is not feasible. Techniques have been used to try to alleviate this issue, such as preventing the operation of high energy consumption devices/systems (e.g., EPAS, climate control) and/or adding a voltage stability source during an auto stop-start or re-cranking operation; however, having certain features not available for use during the engine-off operation may be noticeable to the driver of the vehicle, which may result in customer dissatisfaction or bringing the vehicle in for service calls.
Even for vehicles utilizing a dual battery system, the system may still draw from both batteries (such as an engine re-start operation by a starter motor) thereby depleting both batteries of the energy. Moreover, if a power source drops below a predetermined voltage level, diagnostic trouble codes (DTCs) may be set, thereby issuing a warning light to the driver, or more so, inhibiting further use of the engine stop-start operation which negates the advantage of what vehicles with auto stop-start functionality is intended for, to reduce emissions and increase fuel economy for the driver.